What is a balsa wood tower structure?

According to the Free Dictionary, balsa wood is a strong, lightweight wood used for miniature architectural structures. Model airplanes, cars and buildings are often made of balsa wood. The wood comes from the balsa tree, a native forest tree of lowland Central America.

Balsa lumber is soft and light, with coarse, open grain. In addition to its use in model towers and airplanes, balsa is often used as a core material in full-scale wind turbines. It is a popular wood type for whittling and woodcarvings. Ecuador supplies 95 percent or more of commercial balsa. Most balsa trees are grown on large, densely packed tree plantations.